Making colored biocidal multi-layer structure

ABSTRACT

A method of making a colored biocidal multi-layer structure includes providing a first layer of a first color and locating a biocidal second layer on or over the first layer. The biocidal second layer has a second color different from the first color.

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly-assigned co-pending U.S. patentapplication Ser. No. 14/519,425, filed Oct. 21, 2014, entitled ColoredBiocidal Multi-Layer Structure, by Scheible et al, and tocommonly-assigned co-pending U.S. patent application Ser. No. 14/519,489filed Oct. 21, 2014, entitled Using Colored Biocidal Multi-LayerStructure, by Scheible et al, to commonly-assigned U.S. patentapplication Ser. No. 13/235,789 (now U.S. Publication No. 2013/0071143),filed Sep. 19, 2011, entitled Antibacterial and Antifungal Protectionfor Toner Image, by Blanton et al, and to commonly-assigned U.S. patentapplication Ser. No. 13/357,082 (now U.S. Publication No. 2013/0186301),filed Jan. 24, 2012, entitled Ink Having Antibacterial and AntifungalProtection, by Blanton et al, the disclosures of which are incorporatedherein.

FIELD OF THE INVENTION

The present invention relates to biocidal layers having antimicrobialefficacy on a surface.

BACKGROUND OF THE INVENTION

Widespread attention has been focused in recent years on theconsequences of bacterial and fungal contamination contracted by contactwith common surfaces and objects. Some noteworthy examples include thesometimes fatal outcome from food poisoning due to the presence ofparticular strains of Escherichia coli in undercooked beef; Salmonellacontamination in undercooked and unwashed poultry food products; as wellas illnesses and skin irritations due to Staphylococcus aureus and othermicro-organisms. Anthrax is an acute infectious disease caused by thespore-forming bacterium bacillus anthracis. Allergic reactions to moldsand yeasts are a major concern to many consumers and insurance companiesalike. In addition, significant fear has arisen in regard to thedevelopment of antibiotic-resistant strains of bacteria, such asmethicillin-resistant Staphylococcus aureus (MRSA) andvancomycin-resistant Enterococcus (VRE). The U.S. Centers for DiseaseControl and Prevention estimates that 10% of patients contractadditional diseases during their hospital stay and that the total deathsresulting from these nosocomially-contracted illnesses exceeds thosesuffered from vehicular traffic accidents and homicides. In response tothese concerns, manufacturers have begun incorporating antimicrobialagents into materials used to produce objects for commercial,institutional, residential, and personal use.

Noble metal ions such as silver and gold ions are known for theirantimicrobial properties and have been used in medical care for manyyears to prevent and treat infection. In recent years, this technologyhas been applied to consumer products to prevent the transmission ofinfectious disease and to kill harmful bacteria such as Staphylococcusaureus and Salmonella. In common practice, noble metals, metal ions,metal salts, or compounds containing metal ions having antimicrobialproperties can be applied to surfaces to impart an antimicrobialproperty to the surface. If, or when, the surface is inoculated withharmful microbes, the antimicrobial metal ions or metal complexes, ifpresent in effective concentrations, will slow or even preventaltogether the growth of those microbes. Recently, silver sulfate,Ag₂SO₄, described in U.S. Pat. No. 7,579,396, U.S. Patent ApplicationPublication 2008/0242794, U.S. Patent Application Publication2009/0291147, U.S. Patent Application Publication 2010/0093851, and U.S.Patent Application Publication 2010/0160486 has been shown to haveefficacy in providing antimicrobial protection in polymer composites.The United States Environmental Protection Agency (EPA) evaluated silversulfate as a biocide and registered its use as part of EPA Reg. No,59441-8 EPA EST. NO. 59441-NY-001. In granting that registration, theEPA determined that silver sulfate was safe and effective in providingantibacterial and antifungal protection.

Antimicrobial activity is not limited to noble metals but is alsoobserved in other metals such as copper and organic materials such astriclosan, and some polymeric materials.

It is important that the antimicrobial active element, molecule, orcompound be present on the surface of the article at a concentrationsufficient to inhibit microbial growth. This concentration, for aparticular antimicrobial agent and bacterium, is often referred to asthe minimum inhibitory concentration (MIC). It is also important thatthe antimicrobial agent be present on the surface of the article at aconcentration significantly below that which can be harmful to the userof the article. This prevents harmful side effects of the article anddecreases the risk to the user, while providing the benefit of reducingmicrobial contamination. There is a problem in that the rate of releaseof antimicrobial ions from antimicrobial films can be too facile, suchthat the antimicrobial article can quickly be depleted of antimicrobialactive materials and become inert or non-functional. Depletion resultsfrom rapid diffusion of the active materials into the biologicalenvironment with which they are in contact, for example, water solublebiocides exposed to aqueous or humid environments. It is desirable thatthe rate of release of the antimicrobial ions or molecules be controlledsuch that the concentration of antimicrobials remains above the MIC. Theconcentration should remain there over the duration of use of theantimicrobial article. The desired rate of exchange of the antimicrobialcan depend upon a number of factors including the identity of theantimicrobial metal ion, the specific microbe to be targeted, and theintended use and duration of use of the antimicrobial article.

Antimicrobial coatings are known in the prior art, for example asdescribed in U.S. Patent Application Publication No. 2010/0034900. Thisdisclosure teaches a method of coating a substrate with biocideparticles dispersed into a coating so that the particles are in contactwith the environment. Non-planar coatings are also known to providesurface topographies for non-toxic bio-adhesion control, for example asdisclosed in U.S. Pat. No. 7,143,709.

Fabrics or materials incorporating biocidal elements are known in theart and commercially available. U.S. Pat. No. 5,662,991 describes abiocidal fabric with a pattern of biocidal beads. U.S. Pat. No.5,980,620 discloses a means of inhibiting bacterial growth on a coatedsubstrate comprising a substantially dry powder coating containing abiocide. U.S. Pat. No. 6,437,021 teaches a water-insoluble polymericsupport containing a biocide. Methods for depositing thinsilver-comprising films on non-conducting substrates are taught in U.S.Patent Application Publication No. 2014/0170298.

However, as noted above, the antimicrobial coatings and materials losetheir efficacy over time. Due to the variety of environmentalcircumstances and usage patterns of such anti-microbial coatings andmaterials, it is difficult to know when they are no longer efficacious.

SUMMARY OF THE INVENTION

There is a need, therefore, for an anti-microbial article that isreadily replaced or refreshed in response to a simply observedindication incorporated into the anti-microbial article.

In accordance with the present invention, a method of making a coloredbiocidal multi-layer structure includes:

providing a first layer of a first color; and

locating a biocidal second layer on or over the first layer, thebiocidal second layer of a second color different from the first color.

The present invention provides a colored biocidal multi-layer structurethat provides antimicrobial properties and is readily refreshed orreplaced in response to a simply observed indication.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent when taken in conjunction with the followingdescription and drawings wherein identical reference numerals have beenused to designate identical features that are common to the figures, andwherein:

FIG. 1 is a cross section illustrating an embodiment of the presentinvention;

FIG. 2 is a cross section of a multi-layer structure in anotherembodiment of the present invention;

FIGS. 3 and 4 are plan views of a layer useful in embodiments of thepresent invention;

FIG. 5 is a cross section of a non-planar embodiment of the presentinvention; and

FIGS. 6-8 are flow diagrams illustrating methods of the presentinvention.

The Figures are not drawn to scale since the variation in size ofvarious elements in the Figures is too great to permit depiction toscale.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an antimicrobial article such as abi-layer biocidal structure 5 shown in FIG. 1 of the present inventionthat includes a simply observed indication to replace the article. In anembodiment, the indication is related, either directly or indirectly, tothe antimicrobial efficacy of the article or is otherwise associatedwith the antimicrobial efficacy of the article. The indication isprovided by apparent changes in color of at least portions of thearticle. The changes are, for example, patterns, text, or graphicelements formed in an underlying layer that are exposed as overlyinglayers exposed to the environment are degraded over time. In one methodof the present invention, the antimicrobial article is repeatedly washedand the repeated washing removes portions of the article to expose theindication and indicate that the article should be replaced.

Referring to FIG. 1, in an embodiment of the present invention, thebiocidal multi-layer structure 5 includes a first layer 10 of a firstcolor and a biocidal second layer 20 on or over the first layer 10. Thebiocidal second layer 20 has a second color different from the firstcolor. Any layers, for example adhesive or environmental protectionlayers, located between the first layer 10 and the second layer 20 aresufficiently transparent that the color of the first layer 10 isperceived by an observer through the second layer 10. In an embodiment,the first or second layers 10, 20 are polymer or contain polymers, forexample polymers coated as a liquid or laminated and then cured withheat, drying, or radiation.

In an embodiment, the first layer 10 is located on or over a support 30,for example a substrate such as glass or plastic. In a usefularrangement, the support 30 is adhered, for example with an adhesivelayer 50 such as a pressure-sensitive adhesive or glue such aswall-paper glue, to a surface 8. The surface 8 is any surface 8, planaror non-planar that is desired to resist the growth of biologicallyundesirable organisms, including microbes, bacteria, or fungi. Invarious applications, the surface 8 is a surface of a structure 40, suchas a wall, floor, table top, door, handle, cover, device surface, or anysurface likely to come into contact with a human.

The support 30 is any layer that is capable of supporting the first andsecond layers 10, 20 and in different embodiments is rigid, flexible, ortransparent and is made of a plastic, paper, or vinyl or combinations ofmaterials. The support 30 has a support thickness 36 measured from afirst support side 32 to an opposing second support side 34 that can,for example be adhered to the surface 8. The biocidal multi-layerstructure 5 can form a wall paper.

The first layer 10 has a first-layer thickness 16 measured from afirst-layer first side 12 to an opposing first-layer second side 14 thatis, for example, adhered to the first support side 32. The biocidalsecond layer 20 has a second-layer thickness 26 measured from asecond-layer first side 22 to an opposing second-layer second side 24that is, for example, adhered or cross linked to the first-layer firstside 12. Alternatively, an adhesion layer such as a binder primer layer52 (FIG. 2) is located between the first and second layers 10, 20 toadhere the first and second layers 10, 20 together.

The biocidal second layer 20 is a biocidal layer. By biocidal layer ismeant herein any layer that resists the growth of undesirable biologicalorganisms, including microbes, bacteria, or fungi or more generally,eukaryotes, prokaryotes, or viruses. In particular, the biocidal secondlayer 20 resists the growth, reproduction, or life of infectiousmicro-organisms that cause illness or death in humans and especiallyantibiotic-resistant strains of bacteria. In various embodiments, thebiocidal second layer 20 is rendered biocidal by including chemicalssuch as drugs in the biocidal second layer 20 or by including particles60 such as ionic metals or metal salts in the biocidal second layer 20.The particles 60 reside in the biocidal second layer 20. In anembodiment, some of the particles 60 in the biocidal second layer 20 areexposed particles 62 that extend from the second-layer first side 22into the environment and can interact with any environmentalcontaminants or biological organisms in the environment. Exposedparticles 62 are thus more likely to be efficacious in destroyingmicrobes. In various embodiments, the particles 60 are silver or copper,are a metal sulfate, have a silver component, are a salt, have a sulfurcomponent, have a copper component, are a silver sulfate salt, orinclude phosphors. In an embodiment, the biocidal second layer 20 isthinner than the first layer 10 so that the second-layer thickness 26 isless than the first-layer thickness 16, thus reducing the quantity ofparticles 60 or drugs that are required in the biocidal second layer 20.In an alternative embodiment, the second-layer thickness 26 is greaterthan the first-layer thickness 16.

Referring further to FIG. 2, the particles 60 of the bi-layer biocidalstructure 5 in the biocidal second layer 20 have a variety of sizes, forexample some particles are large particles 64, others are smallerparticles 60, and some of either are exposed particles 62. The particles60 include both the large particles 64 and any exposed particles 62. Inan embodiment, the biocidal second layer 20 has a second-layer thickness26 that is less than at least one diameter of one or more of theparticles 60, has a second-layer thickness 26 that is less than a meandiameter of the particles 60, or has a second-layer thickness 26 that isless than the median diameter of the particles 60. In anotherembodiment, the particles 62 have at least one diameter between 0.05 and25 microns. Suitable particles with such a size range have been made.Alternatively, the biocidal second layer 20 is greater than or equal to0.5 microns thick and the biocidal second layer 20 is less than or equalto 20 microns thick. When the second-layer thickness 26 is less than thediameter of a substantial number of particles 60, some of the particles60 are not necessarily exposed particles 62.

In another embodiment and as shown in FIG. 2, the first layer 10includes particles 60. Alternatively, both the first layer 10 and thebiocidal second layer 20 include particles 60 and the particles 60 inthe first layer 10 are the same kind of particles 60 as the particles 60in the biocidal second layer 20.

Referring to FIGS. 3 and 4, according to embodiments of the presentinvention, the first layer 10 is patterned or has an indicator 70. Theindicator 70 or pattern can be text (for example the word “Replace”),graphic elements, pictograms, or pictures. In an embodiment, thepatterning or indicator 70 is a patterning having the first color.Alternatively, the first layer 10 simply has a different first colorfrom the second color and the different color indicates that thebiocidal second layer 20 should be replaced. Since the biocidal secondlayer 20 can, over time, become ineffective and need to be replaced, thefirst color, the pattern or the indicator 70 indicates that the biocidalsecond layer 20 should be replaced.

In various embodiments, the first color is red (a color of alarm oremergency in many cultures), is darker than the second color (sincedarker colors are associated with dirt in medical environments), or isblack or gray. Alternatively or in addition, for similar reasons in someembodiments the second color is lighter than the first color or is acolor associated in some cultures with cleanliness or purity, such aswhite, blue, or green.

Referring to FIG. 5, in an embodiment the biocidal second layer 20 isnon-planar. Such non-planar layers are made in curable polymer layerswith a stamp using imprinting methods known in the art. As shown in FIG.5, the first and second layers 10, 20 are formed on the support 30. Thenon-planar second layer includes the particles 60 and the exposedparticles 62 and has indentations 80. The indentations 80 form atopographical non-planar layer in the biocidal second layer 20 that isinhospitable to the growth and reproduction of microbes. In yet anotherembodiment, the first or second layers 10, 20 have a hydrophobicsurface, for example by providing a roughened surface either byimprinting or by a treatment such as sandblasting or exposure toenergetic gases or plasmas.

In a further embodiment of the present invention, the first layer 10,the biocidal second layer 20, or the support 30 is or includes aheat-shrink film, for example polyolefin, polyvinylchloride,polyethylene, or polypropylene. Any of the first layer 10, the biocidalsecond layer 20, or the support 30 can include cross linking materialsthat are cross linked for example by radiation or heat to providestrength.

FIG. 6 is a flow chart illustrating various methods of the presentinvention. Referring to FIG. 6, a method of making a colored biocidalmulti-layer structure 5 includes providing the support 30 in step 100and forming the first layer 10 on the support 30 in step 105. In oneembodiment, the support 30 and first layer 10 are the same structureprovided as a single element. The first layer 10 has a first color. Inan optional embodiment, the first color is patterned in the first layer10 in step 110, for example forming text, graphics, graphic elements,pictures, or pictograms. In various embodiments, the support 30 is paperor plastic and the first layer 10 is plastic, for example a polymer or across linkable polymer that is curable. The first layer 10 is patternedin any of a variety of ways known in the art, for example by printingwith ink transfer from a patterned surface or by inkjet patterning. Thefirst layer 10 is formed in various ways, including extrusion orcoating, for example spin coating, curtain coating, or hopper coating,or other methods known in the art. The first layer 10 is cured, ifnecessary, for example by heat or radiation in step 115.

The biocidal second layer 20 is also formed in various methods known inthe art and is a biocidal layer that includes biocidal materials such asdrugs, biocides, or particles 60. The biocidal second layer 20 has asecond color different from the first color. In an embodiment, adispersion of particles 60 is formed in a carrier such as a liquid instep 140 and located on the cured first layer 10 in step 120, forexample by coating, to form the biocidal second layer 20. Making andcoating liquids with dispersed particles is known in the art. In analternative, the biocidal second layer 20 is made separately andlaminated on or over the first layer 10.

Optionally, the biocidal second layer 20 is imprinted in step 125 andcured in step 130 to form the non-planar biocidal second layer 20including biocidal particles 60. Imprinting methods are known in the artand employ a stamp pressed against an uncured layer that is then curedand the stamp removed. Again optionally, a portion of the biocidalsecond layer 20 is removed in step 135, for example to expose theparticles 60 to form exposed particles 62 or increase the surface areaof the exposed particles 62 that is exposed. Removal of portions of thebiocidal second layer 20 is accomplished in step 135, for example, byexposing the biocidal second layer 20 and particles 60 to energeticparticles such as gases or plasma, for example using processes such asetching, plasma etching, reactive plasma etching, ion etching, orsandblasting. Such removal methods are known in the art. In otherembodiments, the biocidal second layer 20 is formed, imprinted, andtreated before it is located on or over the first layer 10, for exampleby lamination.

In step 150, a surface 8 is identified. The surface 8 is a surface whichit is desired to keep free of microbes, for example a wall, floor, tabletop, door, handle, knob, cover, or device surface, especially anysurface found in a any type of medical institution. In an embodiment,the surface 8 is planar; in another embodiment, the surface 8 isnon-planar. In step 155, an adhesive is located, for example on thesurface 8 or on the second support side 34 of the support 30 oppositethe surface 8, to form an adhesive layer 50. The support 30 is adheredto the surface 8 in step 160. In a further embodiment, the support 30,first layer 10, and biocidal second layer 20 are heated to shrink thelayers on the surface 8 if the surface 8 is non-planar. In anembodiment, the heating step (not shown separately) is also the adhesionstep 160 and a separate adhesive layer 50 is not necessary or used. Inan embodiment, the biocidal second layer 20 is thinner than the firstlayer 10. In another embodiment, the biocidal second layer 20 is formedto have a thickness such that the particles 60 extend from a surface(e.g. second-layer first side 22) of the biocidal second layer 20 and aportion of the particle's surface area is exposed. For example, thebiocidal second layer 20 is formed with a thickness that is less than atleast one diameter of one or more of the particles 60, has a thicknessthat is less than a mean diameter of the particles 60, or has athickness that is less than the median diameter of the particles 60.

In a further embodiment, the first layer 10 is a biocidal first layer 10and includes drugs or anti-microbial particles 60. In such anembodiment, the first layer 10 is formed as a dispersion with particlesor a liquid with multiple components that are coated over the support 30or formed into a layer that is laminated to the support 30 or formedinto a free-standing layer on which the biocidal second layer 20 islocated. In an alternative, the biocidal second layer 20 includes one ormore particles 60 in a liquid and the particles 60 self-segregate in theliquid before the liquid is cured. In an embodiment, the particles 60self-segregate after the liquid is coated, for example over or on firstlayer 10, and before the liquid is cured to form the biocidal secondlayer 20. In another embodiment, the self-segregating particlesaggregate at the second-layer first side 22 of the biocidal second layer20.

In another embodiment, the first layer 10 includes one or more particles60, and a method of the present invention further includes forming thefirst layer 10 so that the particles 60 extend from a portion of thesurface of the first layer 10 and are exposed and optionally furtherincluding removing a portion of the first layer surface and increasingthe exposed surface area of the particles 60, for example by etching,plasma etching, reactive plasma etching, ion etching, or sandblasting.

Referring to FIG. 7, in another method of the present invention, thecolored biocidal multi-layer structure 5 is used by first locating thestructure in step 200, for example on the surface 8 on which it isdesired to inhibit the presence of microbes. The colored biocidalmulti-layer structure 5 is observed over time in step 205, especiallywith respect to the structure's color or appearance and the visibilityof the patterns described above (e.g. as shown in FIGS. 3 and 4). Thecolored biocidal multi-layer structure 5 and especially the biocidalsecond layer 20 is periodically cleaned in step 210 to remove dirt andany microbes, alive or dead, on the surface (e.g. second-layer firstside 22) of the biocidal second layer 20. According to variousembodiments of the present invention, the cleaning process of step 210gradually abrades or dissolves the biocidal second layer 20 so that overtime the biocidal second layer 20 is at least partially removed and thefirst color or patterning of the first layer 10 is revealed. As long asthe biocidal second layer 20 remains sufficiently in place, no color orpattern change is observed in step 215 and the periodic cleaningcontinues. Eventually, the color change is observed in step 215 and thebiocidal layer 20 is replaced in step 220.

Replacement can proceed in a variety of ways. According to variousembodiments of the present invention, the colored biocidal multi-layerstructure 5, or portions of the colored biocidal multi-layer structure 5are replaced when the first color of the first layer 10 becomesapparent. In one embodiment, another colored biocidal multi-layerstructure 5 is simply located over the colored biocidal multi-layerstructure 5. Thus, the colored biocidal multi-layer structure 5 becomesthe structure 40 and another colored biocidal multi-layer structure 5 isapplied to the structure 40, for example with an adhesive layer 50 (FIG.1). In another embodiment, the colored biocidal multi-layer structure 5is removed and another colored biocidal multi-layer structure 5 put inits place. As shown in FIG. 1, the support 30 is adhered to thestructure 40 with an adhesive layer 50. Chemical or heat treatments areapplied to the colored biocidal multi-layer structure 5 to loosen,dissolve, or remove the adhesive layer 50 so the colored biocidalmulti-layer structure 5 can be removed and another adhesive layer 50 isapplied to the structure 40. In an embodiment, the colored biocidalmulti-layer structure 5 is peeled from the structure 40 and anothercolored biocidal multi-layer structure 5 having an adhesive layer 50 onthe third-layer second support side 34 adhered to the structure 40.

Alternatively, portions of the colored biocidal multi-layer structure 5are removed, for example at least a portion of the biocidal second layer20 is mechanically separated from the first layer 10. In an embodiment,the biocidal second layer 20 is peeled from the first layer 10.Alternatively, the biocidal second layer 20 is abraded and removed byabrasion from the first layer 10. As the biocidal second layer 20 isremoved, the first color, pattern, or indicator 70 of the first layer 10becomes increasingly visible. In another embodiment, the biocidal secondlayer 20 is chemically separable from the first layer 10 or chemicallydissolvable in a substance that does not dissolve the first layer 10. Ina useful embodiment, a substance that chemically separates the biocidalsecond layer 20 from the first layer 10 or that chemically dissolves thebiocidal second layer 20 is a cleaning agent. In an embodiment, thebiocidal second layer 20 is repeatedly cleaned, for example by sprayingthe biocidal second layer 20 with a cleaning agent and then rubbing orwiping the biocidal second layer 20, and at each cleaning a portion ofthe biocidal second layer 20 is removed to gradually expose the firstlayer 10, the first color of the first layer 10, and the indicator 70.

Referring to FIG. 8 in another embodiment of the present invention,fluorescent or phosphorescent materials are included in the biocidalsecond layer 20 and are illuminated in step 212. The fluorescent orphosphorescent materials respond to ultra-violet, visible, or infraredillumination and emit light that can be seen or detected in step 213 andcompared to a threshold emission value in step 214. Thus, the continuingpresence of the biocidal second layer 20 is observed. When lightemission in response to illumination is no longer present at a desiredlevel, the biocidal second layer 20 is replaced.

According to yet another embodiment of the present invention, thecleaning step 215 refreshes the biocidal second layer 20 so that theexposed particles 60 in the biocidal second layer 20 are moreefficacious. This can be done, for example, by ionizing the particles70, by removing oxidation layers on the particles 60, or by removingextraneous materials such as dust from the particles 70.

Useful cleaners include hydrogen peroxide, for example 2% hydrogenperoxide, water, soap in water, or a citrus-based cleaner. In anembodiment, the 2% hydrogen peroxide solution is reactive to make oxygenradicals that improve the efficacy of particles 60. In variousembodiments, cleaning is accomplished by spraying the second-layer firstside 22 of the biocidal second layer 20 with a cleaner and then wipingor rubbing the second-layer first side 22. The cleaner can dissolve thebiocidal second layer 20 material and the wiping or rubbing can removedissolved material or abrade the second-layer first side 22 of thebiocidal second layer 20 to expose other particles 60 or increase theexposed surface area of exposed particles 62.

The present invention is useful in a wide variety of environments and ona wide variety of surfaces 8, particularly surfaces 8 that arefrequently handled by humans. The present invention can reduce themicrobial load in an environment and is especially useful in medicalfacilities.

The invention has been described in detail with particular reference tocertain embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

PARTS LIST

-   5 bi-layer biocidal structure-   8 surface-   10 first layer-   12 first-layer first side-   14 first-layer second side-   16 first-layer thickness-   20 second layer-   22 second-layer first side-   24 second-layer second side-   26 second-layer thickness-   30 support-   32 first support side-   34 second support side-   36 support thickness-   40 structure-   50 adhesive layer-   52 binder primer-   60 particle-   62 exposed particle-   64 large particle-   70 indicator-   80 indentations-   100 provide support step-   105 provide first layer step-   110 pattern first layer step-   115 cure first layer step-   120 locate second layer step-   125 imprint second layer step-   130 cure second layer step-   135 remove second layer portion step-   140 form dispersion step-   150 identify surface step-   155 locate adhesive step-   160 adhere support to surface step-   200 locate structure step-   205 observe structure step-   210 clean structure step-   212 illuminate structure step-   213 sufficient emission comparison step-   214 detect emission step-   215 observe color change step-   220 replace biocidal layer step

The invention claimed is:
 1. A method of making a colored biocidalmulti-layer structure, comprising: providing a first layer of a firstcolor; locating a biocidal second layer on or over the first layer, thebiocidal second layer of a second color different from the first color;and patterning the first layer or providing an indicator in the firstlayer, wherein the pattern or indicator indicates that the biocidalsecond layer should be replaced.
 2. The method of claim 1, furtherincluding imprinting the first layer or the biocidal second layer. 3.The method of claim 1, further including curing the first layer orcuring the biocidal second layer.
 4. The method of claim 1, furtherincluding providing a support.
 5. The method of claim 4, furtherincluding locating an adhesive on or over the support.
 6. The method ofclaim 4, further including locating the first layer on or over thesupport and the biocidal second layer on or over the first layer on aside of the first layer opposite the support.
 7. The method of claim 1,further including laminating or coating the biocidal second layer on thefirst layer, wherein the biocidal second layer is thinner than the firstlayer.
 8. The method of claim 1, further including forming a dispersionof particles and coating the dispersion on or over the first layer toform the biocidal second layer.
 9. The method of claim 1, wherein thebiocidal second layer includes particles that are silver, copper, have asilver or copper component, is a salt, has a sulfur component, has acopper component, is a silver sulfate salt, or includes phosphors. 10.The method of claim 1, wherein the biocidal second layer includes one ormore particles in a liquid and the particles self-segregate in theliquid before the liquid is cured.
 11. The method of claim 1, whereinthe biocidal second layer includes one or more particles, and furtherincluding forming the biocidal second layer so that the particles extendfrom a surface of the biocidal second layer and have a portion of theirsurface area exposed.
 12. The method of claim 11, further includingforming the biocidal second layer so that the biocidal second layer hasa thickness that is less than at least one diameter of one or more ofthe particles, has a thickness that is less than a mean diameter of theparticles, or has a thickness that is less than the median diameter ofthe particles.
 13. The method of claim 11, further including removing aportion of the biocidal second layer surface and increasing the exposedsurface area of the particles.
 14. The method of claim 13, wherein thestep of removing a portion of the biocidal second layer surface includesetching, plasma etching, reactive plasma etching, ion etching, orsandblasting.
 15. The method of claim 1, wherein the first layerincludes one or more particles, and further including forming the firstlayer so that the particles extend from a surface of the first layer andare exposed.
 16. The method of claim 15, further including removing aportion of the first layer surface and increasing the exposed surfacearea of the particles.
 17. The method of claim 16, wherein the step ofremoving a portion of the first layer surface includes etching, plasmaetching, reactive plasma etching, ion etching, or sandblasting.
 18. Themethod of claim 1, wherein the patterning is a patterning of the firstcolor.
 19. The method of claim 1, further including laminating orcoating the biocidal second layer on the first layer, wherein thebiocidal second layer is thicker than the first layer.